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See Attachment 13-14, Haul Road B Extension Instability Investigation, for documentation of existing <br />conditions including photographs of the area were topsoil was removed and the existing Topsoil <br />• Stockpile H. A confirmation site visit and review was conducted in July 1999 and concluded that no <br />landslides exist in the proposed disturbance area. The results of this confirmation study are included <br />as Attachment 13-6A, Ground Stability Investigation, Yoast Mine and VicinitV• <br />If it is constructed on natural ground, there are portions of the Haul Road B Extension that will exceed <br />10% for greater than 300 feet. Given the existing steep terrain in the "neck" area and SCC's <br />commitment to minimize total disturbance, [he steep grades can not reasonably be eliminated. The <br />only feasible means of eliminating the over-steepened road segments would be to increase the overall <br />road length and add multiple curves or switchbacks. This option is not operationally or <br />environmentally acceptable since the curves or switchbacks would reduce haulage safety and speeds <br />and increased road length would increase surface disturbance. In order to minimize the impact of the <br />steeper sections, culverts will be placed to reduce peak flows from the runoff along the haul road and <br />surrounding disturbed areas. However, erosive velocities will still exist during a 10-year event. Any <br />minor erosion caused by from these infrequent events can be effectively dealt with by routine <br />maintenance of the haul roads and ditches. HauV Road B Extension will be constructed within the <br />lirriits of pit disturbance. Runoff from this area will report to Pond 10. <br />No part of any haul road will be located in the channel of an ephemeral stream draining a watershed of <br />at least one square mile, intermittent or perennial stream unless specifically approved by the Division. <br />• All stream crossings will be made using culverts. Haul roads will be located to minimize downstream <br />sedimentation and flooding. <br />Stream Buffer Zones. Neither the existing or proposed haul roads are located within 100 feet of a <br />perennial stream or stream with a biological community as defined by Section 4.05.18(31 of the <br />CDMG regulations. Road crossings of both Annand Draw and Scotchmans Gulch consist of culverts <br />riprapped at the inlets and outlets. When road ditches route runoff to existing channels, riprapped <br />downdrains are constructed to prevent additional contributions of suspended sediment Isee Tab 16, <br />Protection of the Hydrologic Balancel. <br />Design and Construction. The design of the haul roads incorporate the demand for mobility and travel <br />efficiency, based on the geometric criteria appropriate for the anticipated volume of traffic, weight and <br />speed of the vehicles to be utilized. The design and construction or reconstruction of haul roads not <br />within the estimated disturbed area will be certified by a registered professional engineer, if required by <br />the CDMG for good cause shown. <br />The portions of the proposed haul roads not within the estimated mining disturbance areas will be <br />designed and constructed or reconstructed as described later in this section under "Drainage." <br /> <br />12a Revised 9/99 <br />